PSI - Issue 58

84 Radovan Minich et al. / Procedia Structural Integrity 58 (2024) 80–86 R. Minich et al./ Structural Integrity Procedia 00 (2019) 000–000 5 standard deviations ( =2 ) below the mean curve, provided that log-normal distribution applies, represent a failure probability of 2.3% (this means a probability of survival of 97.7%). The set of already existing S-N curves is permanently supplemented with results from new projects with industrial partners, Fig. 4.

Fig. 4. Opportunity to summarize S-N curves systematically into a database.

The given descriptions of the input information on the fatigue strength of the assessed structural node and its operating load allow a quantitative assessment of the operational fatigue life of new solutions of structural nodes of new bodyworks. And that by comparing it with the information stored in the knowledge base. Fig. 5 shows two limit situations. In green, there is an example of a situation where the assessed structural node of the body is among the high quality in terms of fatigue life, as evidenced by its position among the S-N curves collected in the database. If at the same time, the load spectrum is not aggressive, the developer of the new bodywork can continue the development without worry. The opposite situation is shown in red. The solution of the new structural node is obviously not very high quality compared to the previous solutions. In addition, the load spectrum is aggressive. In such a case, it is necessary to proceed with structural changes of bodywork nodes and to think about how to reduce the level of loading of the developed vehicle. The advantage of the quantitative approach is that it can rely on estimates of the future loading of structural nodes as well as accelerated procedures for determining their fatigue properties. Brauta et al. (2021) and Basan et al. (2023) presented such approaches for other types of structures, but with appropriate modification, it would certainly be possible to use them in fatigue parameters estimation of bus bodyworks nodes as well.